NORTH COUNTY  When you think of horrible traffic, Los Angeles is typically the first region that comes to mind.

But Escondido resident Carolina Cardenas says that’s not the case. Cardenas’ four-day-a-week commute to Cal State University headquarters in Long Beach takes her through San Diego, Orange and Los Angeles counties, and the worst part of her nearly 200-mile round-trip commute usually comes when she’s hitting the brakes in the evening at the end of her day.

“I don’t understand how San Diego County can be worse that L.A. and even Orange County,” she said. “And it’s the hardest part because you’re almost home.”

Not surprisingly, Cardenas is talking about the stretch of state Route 78 near Barham Drive in San Marcos, named the worst rush-hour bottleneck in San Diego County in a U-T San Diego report last month.

Route 78 workshops

SANDAG is holding community outreach meetings to gather comments on a state Route 78 Corridor Study.

For more information or to complete an online comment form and survey, go to sandag.org/sr78study. Information also is available at keepsandiegomoving.com.

“It’s there every day,” said Tim Scott of Mission Hills, who until last month commuted from La Mesa to Carlsbad for his job at sports card company Upper Deck. “I would build it into my schedule. I guess if there’s anything good about it, it’s consistent.”

Indeed, the bottleneck occurred on 98 percent of workdays last year, according to the U-T report.

What is it about the stretch of 78 that brings traffic to a crawl anywhere from 2 to 7 p.m. weekdays?

State Route 78 as the main east-west corridor connecting Interstates 15 and 5 was completed more than 40 years ago. In that time, the populations of the cities along the roughly 17-mile stretch — Escondido, San Marcos, Vista, Carlsbad and Oceanside — have swelled. Housing developments, major shopping centers and colleges have been built, with many of the projects in San Marcos.

Shopping centers and big-box stores line the corridor. Every few miles, drivers pass a Walmart, Costco, Target, Kohl’s, Best Buy, Lowe’s or Home Depot.

Cal State San Marcos opened 22 years ago and now serves 10,000 students. Palomar College, a school with 30,000 students, has its main campus off Route 78 in San Marcos.

The average daily traffic on the Route 78 corridor ranges from 123,000 at the west end to 163,000 near I-15 in Escondido and San Marcos, according to the San Diego Association of Governments, the region planning agency.

In 1990, the San Marcos population was 39,000. It has more than doubled to more than 84,000 today. Over the past 20 years, Escondido has grown from 108,000 to 148,000. Rapid growth has occurred in cities between and beyond, with Route 78 carrying commuters toward jobs and homes in Temecula, Rancho Bernardo, 4S Ranch and San Elijo Hills in San Marcos.